MSNBC’s recent primetime ratings winning streak was halted Monday night as breaking coverage of the explosion around the United Kingdom’s Manchester Arena on Monday shuffled the recent pecking order of the cable-news networks.

Fox News Channel, which saw its usual dominance of primetime upset last week by MSNBC, led Monday night in terms of both viewers between 25 and 54 – the demographic most coveted by advertisers – as well as overall audience, according to preliminary numbers from Nielsen. Fox snared 884,000 viewers between 25 and 54, compared with 729,000 for CNN and 444,000 for MSNBC.

The fluctuating measures suggest that no network’s position is guaranteed in a chaotic news cycle that has sparked rabid consumption of TV news even as it has polarized audiences. MSNBC’s primetime schedule, led by 9 p.m. host Rachel Maddow, handily won last week. The audience spikes appeared to be driven by a series of news breaks surrounding the government’s ongoing investigation into Russian interference with U.S. elections, and suspicion that Trump campaign staffers could have had some involvement. MSNBC and CNN have plunged into the stories, while Fox News Channel’s primetime programs have not.

MSNBC has surged in recent days. The NBCUniversal-owned outlet was the most-watched cable-news network in weekday primetime in both the advertiser demo and overall viewers for the week of May 15th, marking the first time the network has triumphed over both Fox News and CNN in the same week in its history. MSNBC launched as a joint venture between NBC and Microsoft in July of 1996. It also marked the second consecutive week in which MSNBC won in the demo.

For the month of May through the 21st, Fox News continues to lead in the advertiser demo as well as in terms of overall viewers.

Breaking-news coverage tends to upset ongoing trends. Moments of crisis, terrorist attacks and political elections tend to draw out viewers who do not tune in regularly to Anderson Cooper, Lawrence O’Donnell or Sean Hannity.